A number of substances exhibiting in various experimental systems, potent and selective activity in reducing cancer dissemination and metastasis formation without interference on the primary tumor growth, have been found and initially investigated. These studies deal with in vitro and in vivo experiments aimed at an elucidation of the possible mechanism(s) of action of these substances and the site(s) of their activity in the complex interplay of events leading to metastasis formation; at the development of new dissemination models representative of clinically encountered situations, and at the search of new compounds with selective antimetastatic activity.